This disclosure is related generally to method for detecting printing artifacts, and more particularly to a method for detecting artifacts caused by toner reload.
In electrophotographic printing, a charge retentive surface, typically known as a photoreceptor, is electrostatically charged, and then exposed to a light pattern of an original image to selectively discharge the surface in accordance therewith. The resulting pattern of charged and discharged areas on the photoreceptor form an electrostatic charge pattern, known as a latent image, conforming to the original image. The latent image is developed by contacting it with a finely divided electrostatically attractable powder known as toner. Toner is held on the image areas by the electrostatic charge on the photoreceptor surface. Thus, a toner image is produced in conformity with a light image of the original being reproduced. The toner image may then be transferred to a substrate or support member (e.g., paper) and the image affixed thereto to form a permanent record of the image to be reproduced. In the process of electrophotographic printing, the step of conveying toner (“developer”) to the latent image on the photoreceptor is known as “development.”
Two-component and single-component developer materials are commonly used for development. A typical two-component developer comprises magnetic carrier granules having toner particles adhering triboelectrically thereto. A single-component developer material typically comprises toner particles. Toner particles are attracted to the latent image, forming a toner powder image on the photoconductive surface. The toner powder image is subsequently transferred to a copy sheet. Finally, the toner powder image is heated to permanently fuse it to the copy sheet in image configuration. This electrophotographic marking process can be modified to produce color images. One color electrophotographic marking process, called image-on-image (IOI) processing, superimposes toner powder images of different color toners onto the photoreceptor prior to the transfer of the composite toner powder image onto the substrate. Further details of the operation of IOI processing can be found in co-pending, co-assigned U.S. patent application Ser. No. 10/741,715 filed Dec. 19, 2003 to Richard L. Forbes II et al. for “Material State Management Via Automatic Toner Purge”, the contents of which are incorporated herein in its entirety and made a part hereof.
On some color printers, low area coverage (LAC) documents result in reduced developer life. A primary driver of developer life in LAC documents is magnetic roll speed. Reducing magnetic roll speed increases developer life, but leads to an artifact known as reload, which only occurs on some documents. Toner in the housing has an effective age, depending both on magnetic roll speed (aging more slowly for lower speeds) and on residence time in the housing. The effective age of the toner controls the ability of the toner to be developed. Reload artifact results when the toner on the donor roll is not all equally fresh. Currently, reload artifact is controlled by purging the toner regularly during low area coverage documents in order to refresh the toner in the developer housing. This prevents reload but results in lost productivity due to slower printing times and costs for the additional toner that is purged.
20031375-US-NP describes a method for detecting pages subject to reload artifact that does not take into account 101 effects when determining whether there is enough toner removed from the donor roll to cause a reload artifact one revolution later. However, the method in 20031375-US-NP may be overly conservative, since less toner is generally removed in an IOI system. It would be desirable to have method for detecting artifacts caused by toner reload that takes into account the effects of an IOI system.